S-matrices for Planckian scattering

String theory seems to ive a unitary description of physics in the nei hbourhood of certain black holes.A nice example of this is the AdS/CFT conjecture,where processes in the near-horizon region of sev- eral black branes are described by a conformal field theory which is unitary.However,it is hard to understand from the CFT where exactly Hawkin sarument oeswron. An alternative but related pro ram for understanding these issues was started by t Hooft,who considered the near-horizon region of the Schwarzschild black hole,namely flat space.The interactions between outgoin Hawkin radiation and ingoin particles,which near the black hole are boosted to the speed of light,can then be simulated by the gravitational interactions between massless particles.An S -matrix for their scatterin can then readily be computed.For a review on the S -matrix Ansatz we further refer to [1 ]. In this note we discuss the quantum mechanical properties of this model,and its possible relation to the AdS/CFT conjecture